1. Field of the Invention
The invention relates to a speaker apparatus of a bidirectional radiation type capable of radiating acoustic waves in bi-directions.
2. Description of Related Art
There are known speakers of a bidirectional radiation type capable of radiating acoustic waves in two directions, in which a plurality of magnetic circuits are arranged back to back.
As one of the speakers of such a type, there is known a speaker unit capable of achieving an excellent bidirectivity without any deviation of a phase by bringing completely the same movement in two diaphragms by means of, for example, a repulsion type magnetic circuit such constituted that the same poles of two magnets face to each other via a center plate, as disclosed in, for example, Japanese Patent Application Laid-open (JP-A) No. 7-131893.
Furthermore, there is known an acoustic apparatus capable of achieving a reproduced sound field with a sense of realism by controlling an acoustic output ratio of a forward direct radiation sound to a rearward indirect radiation sound, as disclosed in, for example, Japanese Patent Application Laid-open No. 6-98392. There is also known a low-frequency sound reproduction speaker apparatus for a television receiver, in which two speakers are arranged back to back inside a speaker box, each of the speakers being fixed in such a manner as to orient in both of right and left directions, as disclosed in, for example, Japanese Utility Model Application Laid-open (JP-U) No. 4-8590.
However, since the plurality of magnetic circuits need be provided in the above-described speakers, the number of component parts is increased by the number of magnetic circuits, thereby raising a problem of an increase in cost. In addition, in the above-described speakers, vibration is generated in the magnetic circuit by a reaction of the vibration generated in the diaphragm, and further the vibration is transmitted to a case housing the magnetic circuits and the diaphragms, thereby raising a problem of radiation of an abnormal noise such as a chattering noise from the case or the like.